Engine control



J n- 1952 H. A. ALEXANDERSON ET AL 5 5 7 ENGINE CONTROL Filed June 6, 1947 4 Sheets-Sheet 2 INVENTORS HUll/HHD F7. HLEXHNDEREUN HRTHUR H. LE FEBVHE rrows/5y Jan. 29, 1952 H. A. ALEXANDERSON ETAL ENGINE CONTROL 4 Sheets-Sheet 5 Filed June 6, 1947 INVENTORJ HUM/7H0 fl. HL EXHNUEHEUN HRTHUR H. LE FEBVHE 5% K/vm Patented Jan. 29, 1952 ENGINE CONTROL Howard Allan Alexanderson, Wood-Ridge, and Arthur Hibbard Le Febvre, Hackensack, N. 1., assignors to Bendix Aviation Corporation, Teterboro, N. J., a corporation of Delaware Application June 6, 1947, Serial No. 752,912

18 Claims. (Cl. 121-41) The present application relates to improvements in control mechanisms for power units of aircraft particularly of a type such as shown in the copending application Serial No. 596,472, filed May 29, 1945, by Howard A. Alexanderson and Robert Z. Hague.

An object of the invention is to provide novel means for effecting sequential control of a supercharger from a low speed hydraulic drive to a high speed hydraulic drive.

Another object of the invention is to provide a novel atmospheric pressure responsive means for limiting the maximum permissible pressure setting of the regulator in accordance with variations in altitude.

Another object of the invention is to provide a novel hydraulically operated means for controlling the intake manifold pressure of an aircraft engine.

Another object of the invention is to provide a novel reset follow-up arrangement for controlling a hydraulic variable speed drive. In the aforenoted copending application, the signal employed was the displacement of oil in the servodecrease line from a flow metering valve. In the present invention the servo-increase to servo-decrease differential is used as the signal for operation of the follow-up piston. Any movement of the flow metering valve caused by a change in servo differential results in a proportional change in the position of the follow-up piston. Resetting involves the valving of servo-increase pressure to the underside of a reset piston which is larger in effective area than the follow-up piston. A follow-up piston spring acts between the two pistons so as to permit servo-increase pressure suitably valved by-the follow-up valve, to move the reset piston and follow-up piston as a unit back to the position corresponding to the desired pressure setting.

Another object of the invention is to provide an improved power reset and altitude droop mechanism over that shownin the aforenoted copending application SerialNo. 596,472.

Another object of the invention is to combine the functions of altitude droop and power reset so that they both limit the maximum permissible pressure setting through the action of a walking beam which links the same so as to stop a pressure selector linkage. Thus, when the pilot, through movement of a pilots control lever, selects a pressure higher than the permissible valve, the selector system is stopped at the maximum value.

Another object of the invention is to provide a novel altitude bellows assembly. Changes in alti- 2 tude pressure result in a movement of the bellows which is transmitted by a linkage to a positioning valve slidably mounted on the stem of an altitude droop piston and arranged to control ports in the stem for affecting the operation of the piston.

Another object of the invention is to so arrange the altitude droop, power reset, and reset followup as to jointly aifect through the action of a zialking beam the pressure setting of the mecha- Another object of the invention is to so arrange the reset follow-up mechanism that when the pilot is controlling the intake manifold pressure merely by throttle, rather than by the speed of the supercharger, the reset follow-up mechanism may be automatically cut out of operation- Another object of the invention is to provide a novel reset follow-up valve and piston. structure in which the piston stem serves as a control valve Figure 1 is a diagrammatic view of the novel hydraulic control system;

Figure 2 is a diagrammatic view of the control mechanism shown in Figure 1;

Figure 3 is an enlarged sectional view of one form of the reset follow-up mechanism;

Figure 4 is an enlarged sectional view of another form of the reset follow-up mechanisrnf and Figure 5 is an enlarged sectional view of the altitude droop and power reset mechanism.

\ Referring to Figure 1, there is provided in the present invention a main pilot's control lever I. which is connected by a link 2 to an operative control lever 3. The control lever 3 is: keyed to a main control shaft 4 shown in Figure 2 which extends into the main control unit or regulator indicated in Figure 1 by the letter A andshown diagrammatically in Figure 2 for controlling the setting thereof.

As shown in Figure 1, an engine it drives through a shaft and a multi-speed hydraulic coupling 3|,- a supercharger 32.

The coupling 3| includes a gear 33 keyed in the shaft 30 and driving high speed coupling gear 34; low speed coupling gear 35 and an intermediate speed coupling gear not shown.

The high speed coupling gear 34 drives through a shaft 33 rotatably supported by a bearing 31 one set of blades of a hydraulic coupling 39 of conventional type. The opposite cooperating blades of the coupling 39 are fastened to a driven shaft 4| rotatably supported by a bearing 42. The shaft 4| has a fluid inlet passa e 43 leading into the coupling 39 from a fluid conduit 44 controlled by a regulator A so as to vary the slippage of the coupling 39 as will be explained hereinafter. There is further provided in the casing of the fluid coupling 39 a fluid outlet port through which the hydraulic fluid may be returned from the coupling 39 toa suitable sump not shown.

Keyed to the driven shaft 4| is a high spee 4 35 operably connected. as shown in Figures 1 and 2, to a throttle control arm 33 of the regulator A. The throttle control arm 63 is keyed to a shaft I2 rotatably mounted in a bearing formed in the arm'30 connected through a link 8| to one end casing of the control unit A. Rotatably mounted in the shaft 12 is one end of the shaft 4.

There is provided a servo piston 14 for operatof a walking beam 82. The opposite end of the gear 45 which drives through-a gear 48 thedriv shaft 41 of the supercharger.

The low speed coupling gear 35 drives through a shaft 43 rotatably supported byv a bearing49 one set of blades of a hydraulic coupling 5| hay-Q ing a suitable fluid outletport formed in the casing thereof. The opposite cooperating blades of the coupling 5| arefastened to adriven shaft 53 rotatably supported byjabearing' 53A. The shaft 53 has a fluid inlet passage 54 leading into the coupling 5| from a fluid conduit 55 supplied with oil by a suitable engine driven pump so as to affect the slippage of the coupling. The latter passage is controlled by a valvepositioned within the casing of the coupling 5| which may be of a type such as shown in Hobbs et al., U. S. Pat. No. 2,400,307, granted May 14, 1946, and arranged so that when the driven shaft 53 rotates at a speed greater than the driving shaft 43, the passage 54 is closed so as to permit the supercharger 32 to be driven through either the intermediate or the high speed coupling.

The intermediate speed gear, not shown, drives through a shaft 55 rotatably supported by a bearing 56 one set of blades of a hydraulic coupling 51 of a similar type to coupling 5|. The opposite cooperating blades of the coupling 51 are fastened to a driven shaft 53 rotatably supported by a bearing 53A. The shaft 58 has a fluid inlet passage 59 leading into the coupling 51 from a fluid conduit 30 controlled by a regulator A so as to vary the slippage of the coupling, aswill be explained hereinafter. The latter passage is also controlled by shut off valve positioned within the casing of the coupling 51 which may likewise be of; a type such as shown in Hobbs et a1. U. S. Pat. No. 2,400,307, granted May l4, 1946, and arranged so that when the driven shaft 42 rotates at a speed greater than the driving shaft 55, the passage 59 is closed so as to permit the supercharger 32 to be driven solely through the high speedcoupling 39.

While the low speed and intermediate speed couplings 5| and 51, respectively, each include a shut off valve for the coupling fluid, as explained, the flow of fluid to the high speed coupling 39 is merely controlled by the regulator A.

In the engine systemof Figure 1 controlled by the regulator Aythere is provided a conduit 6| leading from an airscoop through a carburetor 62 into the air inlet for the supercharger 32. A conduit 33 leads from the air outlet of the supercharger 32 to the intake manifoldof the engine 23. A throttle valve 64 controls the air inlet conduit 6|.

The throttle valve 54 is controlled by a rod 73 walking beam 32 is connected through a link 33 tothe arm 19.

Pivotally connected at a point intermediate the opposite ends of the walking beam 82 is one end of a lever arm 34 which is aiflxed at the opposite end to a shaft 35.

The shaft 35 is rotatably supported in suitable bearing portions 38 formed apart of the control unit A. Freely rotatable on the shaft 35 is an arm 33. The arm 33 is pivotally connected at the free end to a rod 39 which connects the arm 33 to a piston 90. The latter piston is slidably mounted in a cylinder 9| into which opens at one end a passage 92 leading to a fluid pressure line such as oil under engine pressure. The piston 90 is normally forced under pressure of theoil in an upward direction as viewed in Figure 2.

A spring 93 is positioned between the piston and the upper end of the cylinder so as to force the piston in a downward direction upon oil pressure failure, whereupon the arm 88 is forced in a clockwise direction. An adjustable screw 94 projects through the arm 83 and is arranged so as to engage an abutment plate 95 on the arm 34 in the latter event so as to restrain movement of the arm 34 in a counter-clockwise direction. A stop pin 95 projects from a portion 9'! of the casing of the unit A so as to restrain the arm 34 from movement in an opposite direction.

The pilot's control lever may their effect manual control of the throttle valve 34 through shaft 4,-arm 80, link 3|, walking beam 82, link 33, arm 19 and throttle control shaft 12.

The adjustable screw 94 is preferably adjusted so as to permit a small amount of angular travel of lever 84 between screw 94 and stop pin 93. During such manual operation of the throttle 64, lever arm 84 is driven between its restraining stops 94 and 96 rotating shaft 35.

At the opposite end of the shaft 85 there is aflixed an arm 98 through which projects an adjustable screw 99. The screw 99 is arranged to engage an arm |0| supported on shaft 35. The armIIlI is freely rotatable on the shaft 85 and hascoupled thereto a push rod I02 which is slidably mounted in a bracket '03. The bracket I03, riveted to the inner wall of the unit A, guides the push rod I02 and supports a coil spring I04 against which the push rodreacts. The spring I04 biases the push rod I02 in an upward direction and the arm |0I in a counter-clockwise direction into engagement with the set screw 99. There is aflixed at the lower end of the push rod I02, a hook-like actuating element I05, which is arranged to cooperate with a pin I06 projecting from the head of a valve stem II3, as described and claimed in the copending application Serial No. 709,923 of Charles E. Cole, filed November 15, 1946, and now U. S. Patent No. 2,444,185, granted June 29, 1948, and assigned to Bendix Aviation Corporation. 1

The valve stem H3 is biased under force of a spring H4 in an upward direction. The valve stem H3 has valve members H5 and H6 arranged'so as to control passages 16 and 11 respectively opening into valve chamber II! and leading to chamber 15 at opposite sides of piston 14 so as to control the movement of the piston 14. The fluid pressure line 92 leads through an oil filter 92A to a point intermediate the openings of-passages 16 and 11 to valve chamber III. A fluid medium outlet or drain passage II8,also opens-from the valve chamber I01 at the lower side of valve II6.

. Another valve chamber I20 is provided separated from the valve chamber III by a sealing member I2I. Projecting through the sealing member I2I is a valve stem I22. At the lower end of the valve stem I22 is mounted a cylindrical valve I23 having a spring I24 which tends to bias the valve I23 and stem I22 in an upward direction.

The fluid pressure passage 92 opens into the opening into the chamber IIO but closed by the valve I23 when biased downward to the position shown in Figure 2. A main drain passage I21 opens into the valve chamber IIO. During normal operation, the fluid medium is drained from the housing by suitable ports not shown.

When no pressure medium is available, or upon oil pressure failure, the drain valve I23, which is loaded by spring I24, is moved in an upward direction under force of the spring I24 serving two purposes. It causes the oil in the housing of the control unit A to drain to a predetermined low level by uncovering drain port I26 so as to permit such drainage through port I25, passage II8, port I26, valve chamber I 20, and through passage I21 to the fluid outlet. Secondly the spring I24 urges valve stem I22 upward into contacting relation with the lower end of the valve stem II3, so as to actuate the valve stem I I3 in an upward direction.

During such fluid pressure failure, movement of the pilots control lever I so as to move arm 60 in a counter-clockwise direction causes movement in a counter-clockwise direction of the lever arm 84 between its restraining stops 96 and 94 whereupon valve stem I22 under force of spring I23 causes servo valve II3 to move from its neutral position, as shown in Figure 2, to an upper position so as to uncover the ports leading to passages 16 and 11 so as to permit movement of the throttle 64 manually. Similarly, upon moveevent slight pressure be available, such movement of the valve II3 directs such slight pressure so as to effect piston 14 so as to assist the manual movement of the arm 10 and thereby assist in the manual control of throttle valve 64.

Automatic control of throttle When fluid pressure is available in excess of a predetermined value,the piston 30 is moved upward under the pressure medium from passage 92 against the force of spring 03. This latter action forces link 80 upward moving lever 88 in a counter-clockwise direction so as to permit lever arm 84 to move free of the restraining screw 94. Likewise, upon such fluid pressure medium becoming effective, the valve I23 is moved downward against spring I24 permitting the servo valve II3 to move free of the valve stem I22 under automatic control.

In order to effect the latter automatic control, there is provided a pressure responsive bellows assembly including an evacuated bellows I3I supported at one end by the inner wall of the control unit A.

A spring I34 is positioned within the evacuated bellows I3I tending to expand the same. At the opposite end of the bellows I3I there is provided a movable arm I35 interposed between the bellows I3I and a second bellows I36. The bellows I36 is mounted at the opposite end by a fixed plate I31 fastened to the control unit A. An adjustable pin I38 projects into the bellows I36 from the portion I31 so as to limit the extent of contraction of the bellows I36 for a purpose which will be described hereinafter.

A passage I39 formed in the control unit A leads from the interior of the bellows I36 to the air intake manifold conduit ,58 as shown in Figure 1. Thus, the bellows I36 is controlled by the intake manifold pressure of the engine 26.

As shown in Figure 2. the movable arm I35 between the manifold pressure bellows I36 and evacuated bellows I3I is connected through a pivot pin I40, link I4I, resilient link assembly I42, and beam I43 to the servo valve H3. The resilient link assembly may be of the type described in the copending application Serial No. 709,923, flled November 15, 1946, by Charles E. Cole, and is arranged so as to permit deflection of the servo valve II3 by the actuating element I05 and valve stem I22 without excessively loading the bellows assembly.

The selected pressure or datum of the bellows assembly may be changed by moving a. pin I44 on which beam I43 is pivotally supported. Pin I44 is linked to one end of a whiIile-tree type of beam I45 controlled through operation of a pressure selecting mechanism, a hydraulic follow-up mechanism, and an altitude droop mechanism as will be described hereinafter.

It will be readily seen, however, from the foregoing, that upon an increase in the intake manifold pressure above the selected pressure there will result an expansion of the manifold pressure bellows I36 causing the beam I43 to be shifted in a clockwise direction whereupon the servo valve II3 will be adjusted upward causing a pressure medium to be' applied through the passage 16 to the upper side of the piston 14 and exhausting the lower side through. passage 11. This action will cause the piston 14 to be adjusted downward so as to adjust the arm 19 in a counter-clockwise direction so as to adjust the arm 6| in a counter-clockwise direction moving valve 64 of Figure 2 through rod 65 in a valve amass? 1 closing direction decreasing the intake manifold pressure until the valve H3 is returned to a neutral position. An opposite effect is, of course. produced upon the intake manifold pressure dropping below the selected valve.

Pressure selecting mechanism tor plate I50 and limits the clockwise rotation of lever I40. The selector plate I50 pivoted on the pin I52 transfers adjustment thereof to the whiille-tree I45 through an interconnecting pin I56 projecting from the plate I50 and upon which the whiflle tree beam I45 is pivotally mounted. It will be readily seen from the foregoing that with spring I48 pivoting lever I48 at follower I41 in a clockwise direction into contacting re lation with adjustment screw I55, the follower I41 and selector plate I50 act as a unit, and the pressure selection of cam I40 is transmitted to the bellows and valve linkage through pin I50. beam I45 and pin I44. I

The manifold pressure bellows I36 is provided with the adjustable lock out stop pin I30 previously described. The latter pin I35 may be adjusted to a low manifold pressure value below the minimum idling pressure for the engine 20.

but above the minimum selected pressure. Thus, as pressures are selected by the pilot through operation of the control lever I which are less than the lockout setting pressum, the control unit A may be locked into manual operation through the joint effect of the pin I38 and I44 causing the adjustment of the valve III upward tending to adjust the throttle valve 64 to a closed position. Through appropriate manual adjustment of the control lever I and a direct follow-up action of rod I02, the throttle 64 may be manually controlled as set forth in the copending application Serial No. 709,923, filed November 15, 1946, by Charles E. Cole and now U. S. Patent No. 2,444,185,.granted June 29, 1948, and'assigned to Bendix Aviation Corporation. The lockout stop 8 diiferential from passage 11 to 10 will rise above the predetermined pressure value.

A metering piston-valve I is provided slidably mounted in a piston chamber IOI openingat one end into the chamber and so arranged that the fluid pressure medium applied to the piston 14 through passage 11 may be also applied to one side of the piston head I00. The piston valve I00 includes the valve members I03 and I04. A passage I06 extends through the valve I00 and opens at opposite sides at IO0A and I003. The

opening IO0B opens into a channel IO0C of the valve I00. A spring I01 biases the piston-valve assembly I00 upward. An adjustable pin I00 projects upward from the valve casing and limits movementof the piston valve I00 in a downward direction, while a ring I08 limits movement of the I36 .also permits closing of the throttle 04 in the event of a broken evacuated bellows, since it provides means for placing the control unit into manual operation. The aforenoted lockout feature is described and claimed in the copending application Serial No. 550,646, filed August 22, 1944,

by Howard A. Alexanderson and now U. S. Patent'No. 2,453,650, granted November 9, 1948, and assigned to Bendix Aviation Corporation.

Supercharger speed control 20 p. s. i. When the piston 14 has opened the throttle 04 fully, if the manifold pressure still remains less than the setting, the fluid pressure piston valve I in an upward direction.

The valve members I03 and I04 are arranged to open in sequence passages I10 and Hi to pressure medium supplied the valve I00 through pres-.

sure conduit I12 as the pressure supplied at one end of piston valve I60 through passage 11 exceeds predetermined differential values above the pressure supplied the opposite end of the valve I60 through passage I15, which opens from the line 16.

The passage I10 opens into the conduit 00 which, as shown in Figure 1, supplies fluid. medium to the intermediate speed coupling 51 through passage 59 and suitable shut off valve not shown. Similarly, the passage I'II opens into the conduit 44 so as to supply fluid medium to the high speed coupling 38 through passage 43.

The hydraulic couplings 51 and 38 serve to couple the driving member 30 to the driven member 41 at varying'speed ratios depending upon the rate of fluid flow supplied to the individ-' ual coupling which thus determines the slippage of the coupling and its speed ratio.

The metering piston-valve I60 is adjustably.

'positioned bythe aforenoted diilerential pres- In order to provide a substantially constant pressure in the passage I12, there is provided a reducing valve I00 including a valve chamber I8I having a pressure inlet passage I02 leading from the piston chamber 8| and an opening in the chamber I8I leading to the passage I12. A spring I85 biases the valve I80 in an upward direction tending to counterbalance the pressure applied at the upper end of valve I80 through a passage I86, while a portion of the valve I80 tends to open the passage I82 to the pressure medium as l the valve I80 is biased upward by the spring I80 so as to increasethe pressure applied through passage I12 to a predetermined constant value. The tension of spring I85 may be adjusted by means of a suitable adjusting mechanism I31 so as to vary the maximum flow through passage I12.

It has been found, however, that there is considerable variation in the back pressure in lines I10 and HI, thereby causing a metering error.

' fluid or oil pressure diiferential of, for example.

In order to correct this condition, a shuttle valve I00 has been provided to connect through conduit IOI the pressure in the passage I10 of the intermediate speed coupling 51 to the lower end of the valve member I00 during intermediate speed supercharger. operation and the pressure in the passage I1I to the lower end of the valve amass-z .0 member I during high speed superchargeroperation. ,As back pressure increases the valve I30 will tend to increase the opening of the passage I82 so as to compensate for such increase.

' through a suitable valve port to'conduit I3I.

However, upon the valve I30 moving downwardly sufliciently so that channel I000 coincides with port IN, the back pressure in line "2 decreases sumcientlv so that shuttle valve I30 is biased under force of spring I32 to the right closing conduit "0 to conduit I3I and connecting conduit m w conduit I3 I' through a suitable chan nel formed in the'shutt le valve" I30. I

lower side of follow-up piston 202 -is the sert 0- decrease pressure line 10, while the upper side of the follow-up piston 202 is subject to the servoincrease pressure line H.

The valve rod 204 has a valve portion 205 which controls a passage 200 leading to a chamber 201 at the lower side of the reset piston 203. The upper side of the reset piston 203- is subject to the pressure in line 16.

Opening at the lowerside of the valve portion 205 is a drain passage 203, while opening at the Conversely, when the pressure in passage I12 exceeds a predetermined value, as upon valve I60 closing passage I II, the valve I30 is shifted to the left so as to shift the reference pressure for the reducing valve I80 from that in passage III to the pressure in passage I30.

The foregoing structure is described and claimed in the copending application Serial No.

596,472, filed May 29, 1945, by Howard A. Alexanderson and Robert Z. Hague.

The present application relates to novel fea-' tures which will be described hereinafter.

Follow-up mechanism When'valve I 00 is moved from. one position to another, there is an elapse of time required to flow the fluid mediuminto the hydraulic coupling 33 or 51 to bring the coupling to": the particular slip condition required, and for the supercharger to cause the intake manifold pressure to rise to the selected value. This time lag tends towards instability and in order to provide a stabilizing action, a novel follow-up mechanism 200 has been provided.

The principle of reset follow-up stabilization of a variable speed drive was originally employed in the earlier disclosure of the application Serial No. 596,472 referred to above. In

, the previous form of reset follow-up, the signal employed. was the displacement of oil in the servo-decrease line corresponding to line I0 leading from the flow metering valve I I3. In the control of the present application the servo-in-.

crease line 11 to servo-decrease line I8 differential isused as the signal for operation of the followup mechanism 200 which may be of a form such as shown in detail in Figure 3 or 4.

' The structure of the reset follow-up mechanism" 200 permits servo-increase pressure to be suitably valvedby a follow-up valve so as to move a reset piston and follow-up piston as a unit back to a position corresponding to the desired mani-,. fold pressure setting. The pressure applied to, the underside of the' reset piston is vented to connected to one end of a valve rod 204 which in turn is connected at the opposit end to an end of the whiflie-tree type of beam 145 to provide a follow-up action to the metering valve II3.

Opening into the valve chamber I at the upper side of the valve portion 205 is the servo pressure increase line. H.

The follow-up piston 202 has a smaller diameter or surface area than the reset piston 203. I The follow-up piston 202 and reset piston 203 are interconnected by a resilient spring member 2I0. There is also provided a stop rod 2 having a portion 2I2 to limit the extent of movement of one piston-relative to the other as will be explained.

An adjustable screw 2I3 limits the downward movement of the reset piston 203.

In operation it will be seen that upon the bellows I34 calling for an increase in the speed of supercharger 32 as upon a decrease in the intake manifold pressure, the valve II3 will be adjusted downward increasing the pressure in line 11 and causing follow-up piston 202 to move downward, whereupon the beam I will pivot about the pin I in a counter-clockwise direction raising the valve I I3 in a follow-up action.

Likewise, the downward movement of valve rod 204 will cause valve 205 to open passage 200 to the pressure line 11 causing reset piston 203 to move upward so as to increase the tension of spring 2I0 and thereby tend to return piston 202 and valve 205 to a neutral position. The latter action likewise resets the beam I45 and the setvalve 205 to open passage 200 to drain 200 and moving beam I45 in a clockwise direction so as to lower valve H3 in a follow-up action. The upward movement of valve 200 will moreover decrease the pressure applied at 201 to cause a reset of piston 203, decreasing the tension applied by spring 2| 0 to piston 202, whereupon piston 202 will be reset downward to a neutral position.

A furtherieature of the reset follow-up arrangement is the mechanical interconnection of the follow-up piston 202 and reset piston 203. During operation of the throttle piston 14, the condition of positive difierential of the servo pressure line 11 minus servo-decrease pressure lin I6, becomes a negative differential, when the pressure 01 line I3 exceeds that of line IT in operating the piston I4 between extreme adjusted positions thereof. Under this condition the pressure in line I6 acting on the piston 202 and 203 tends to cause the same to separate, whereupon valve 205 opens chamber 201 to drain. I'helatter movement of piston 202 in an upward direction islimited by the portion 2I2 of the stop rod 2 which then mechanically connects the two pistons together.

As the piston 203 has a greater surface area than the piston 202, the pressure acting on piston 203 draws the piston 202. downward with it to a point limited by an adjustable screw 2 .e which 11 such that the valve 205 closes passage 206 and rod 204 is held at a neutral position relative to'the beam I45 during throttle operation, a

A second form of the follow-up reset mechanism is shown in Figure 4 in which like numerals with the addition of the letter A indicate corresponding ports to those described with reference to Figure 3 and in which the pistons 202A and 203A areshown in the lock out position assumed during throttle operation.

In the latter form of the invention, there is provided an improved reset control valve arrangement in which'valve rod 204A is slidably mounted in a valve chamber 2 I4 having pressure ports 2I5 opening through suitable passages to passage 206A leading to reset piston chamber 201A and drain ports 2I6 likewise opening to passage 200A.

The valve rod 204A has provided valve members 220 and 22I which serve to control the opening of a pressure passage 222 and a drain passage 223 respectively to the valve chamber 2I4. The pressure passage 222 opens to the upper end of the follow-up piston 202A and thereby to the servo-increase pressure passage HA, while the drain passage 223 opens to the interior of the unit A from which it is drained by suitable means not'shown.

The valve rod 204A has further provided a metering land 225 which is spacedfrom the inner wall of the valve chamber 2l4 and arranged so as to effect a relatively slow rate of flow to the reset chamber 201A through valve chamber 2I4 upon relatively slight movement of valve member 220.

in a direction opening pressure port 222.

The valve rod 204A has also provided a second metering land 226 which is also spaced from the inner wall of the valve chamber 2 I4 and likewise arranged so as to efiect a relatively slow rate of flow from the reset chamber 201A through valve chamber 2I4 upon relatively slight movement of valve member 220 in a direction opening drain port 223. Also affixed to the rod 204A and slidably mounted in the valve chamber 2I4 is a land 22'! positioned in sealing relation in the valve chamber 2 I4 and intermediate the metering lands 225 and 226 so as to separate the pressure and drain passages in the valve chamber 2 I 4.

Thus, the metering lands 225 and 226 provide a convenient means for controlling the rate of flow to and from the reset chamber 201A.

There is further provided a pressure by-pass passage 228 which opens at'one end to passage 206A, while the opposite end thereof is arranged so as to be connected to passage 222 by valve 220 opening passage 228 upon an extreme increase in the pressure effecting line 'I! or differential across lines 11 and I6. Thus, chamber 201A may be connected directly through passage 228 to the source of pressure without being subject to the metering,

action of land 225 upon such extreme change.

There is also ,provided a by-pass drain passage 229 which opens at one end to passage 206A, while the opposite end thereof is arranged so as to be connected to passage 223 by valve member 22I opening passage 229 upon anextreme decrease in the pressure effecting line 11 or the differential across lines 11 and I6. Thus, chamber 201A may be connected directly through passage 229 to 202A Is effected the operating liquid will pass through the clearance provided by the metering land 226 or 225 so as to'cause the reset piston- 203A to return the follow-up piston 202A relatively slowly to a neutral position through action of spring 2IOA.

However, when a great increase in the intake manifold pressure is required, the metering valve I60 will be subjected to a high pressure diiferential across lines I6 and 11 by the servo valve II3. thus causing the metering valve I60 to move downward rapidly and the follow-up piston 202A likewise to move downward to its full extent. The latter action will open by-pass passage 228 so as to cause the reset piston 203A to return the fol- I low-up piston 202A toward a neutral position rapidly and permit the pressure medium to be valved into the coupling passages I10 or III, respectively, to provide acceleration of the couplings 39 and 5! without the retarding effect of the follow-up action.

The follow-up action of the piston 202A is transmitted by rod 204A to the selector whitlietree beam I4'5A. Thus, upon the pressure diiferential across lines I6 and I1 increasing and causing the metering valve I60 to move downward to increase the manifold pressure, the follow-up piston 202A moves downward causing the whiflietree selector beam IA to move in a counterclockwise direction about the pin I56 so as to decrease the pressure setting. Likewise, upon the pressure differential across lines 16 and II increasing, causing the metering valve I60 to move in 'anupward direction to decrease the manifold pressure, the follow-up lever is moved so as to increase the pressure setting and thereby providing a novel follow-up action for preventing instability of the control unit A. However, upon a relatively great change in the intake manifoldv pressure being required, the reset piston 203A is so controlled as to rapidly cut out of operation the latter follow-up action of piston 202A as explained.

drain without being subject to the metering ac- &

tion of land 226 upon such extreme change.

The foregoing feature thus varies the time of resetting with operating conditions so as to tend towards a more stable control.

It will be seen then that during operation when only partial movement or the follow-up piston and power reset In the'ffsubjectlcontrol, the functions of altitude droop andfpowerreset for water injection operation have, been combined in a mechanism 300 so that both limit the maximum permissible intake manifold pressure.

As shown in Figure 2, a walking beam 30I links an altitude droop plunger 302 and a power reset plunger 303 to a push rod 304 slidably mounted in a bracket 305 amxed to the inner surface of the unit A. The push rod 304 is arranged so as to limit the movement of, an arm 306 which, as shown by dotted lines in Figure 2, is affixed to the selector plate I50 so as to limit the adjustment of the manifold pressure selector linkage. Thus, when the pilot, through movement of the pilot's control lever I, selects a pressure higher than the permissible value, the push rod 304 engages the arm 306 and further adjustment of the selector plate I50 in a pressure increasing direction is thereby prevented, the selector system is stopped at the maximum permissible value and the selector cam I46 causes lever I48 to disengage the screw I55 of the selectorplate I50 against further restrict port at whereupon -y pressure applied to piston 321 is increasedfr'nov-t 7 'ing the piston 321 together with plunger 302 and tion 312 from passage 301. The passage 3 l3 leads to the upper side of a piston 3i6, while the passage 3 leads to the upper side of a piston-3| 1.

A spring 3" biases the piston 3I6 upward in opposition to the pressure in line 3i3 while a spring 3l9 biases the piston 3|1 upward in opposition to the pressure in line 3. A stop rod 320 limits the movement of piston 3 i 6 under the force of the spring 3i8 while stop rod 32l limits the movement of piston 3" under the force of spring 3l9. I

The stop rod 32! includes an actuating rod portion 325 which engages the inner end of the power reset plunger 303 and thereby limits its movement, while the stop rod 320 includes an actuating rod portion 326 which limits the downward movement of a servo piston 321.

The passage 3l5, as shown in Figure 2, is connected to a conduit 322 which leads to a valve 323 operated by a solenoid 324 and arranged upon deenergization of the solenoid to open the end of the conduit 322 so as to permit the pressure fluid from line M to drain to the interior of the unit A from which it is suitably drained.

Upon energization of the solenoid 324, the valve 323 is operated so as to close the end of conduit 322 and permit pressure to build up in the conduits 3i3 and 3H forcing the pistons 9l6 and 3H downward against the biasing force of springs 3 l 8 and 3 I 9 respectively.

The servo-piston 321 has, acting at the underside thereof, pressure from the line 309, while a spring 323 biases the piston 321 downward in opposition to the pressure from line 309.

Afllxed to the piston 321 is a hollow stem portion 329 having a passage 330 extending longitudinally therein. One end of the passage 330 opens through ports 33! to the pressure passage 309, while the opposite end of the stem 329 opens through a port 332 to the interior of the unit A from which the exhausted servo fluid may be suitably drained.

Slidably mounted on the stem 329 and controlling the port 332 is a valve 333 afllxed to one end of an arm 334. The arm is pivoted on a pin 335 while the opposite end is connected to an altitude bellows assembly 336.

333, the bellows 331 being evacuated and having a spring 339, while the other bellows 338 is subjected to the pressure to be measured. One end of bellows 331 is fixedly mounted by a bracket 340 while the end of the bellows 338 is fixedly mounted at 34!. The opposite ends of the bellows 331 and 338 bear upon a roller member 342 afllxed to piston 321 assembly.

Operating liquid under pressure, after passing" through restrictions 308 and 3, is fed to the underside of the altitude droop piston 321 to oppose the action of a spring 328 which acts on top of the piston 321. Thus, upon a decrease in atmospheric pressure, as upon a rise in altitude, bellows 338 contracts causing the valve 333 to The bellows assembly consists of two opposed bellows 331 and push rod 304 upward'further limiting the permissible pressure. Of course, upon an increase in atmospheric pressure, an opposite result is effected. I

The action of theassembly 300 is to reduce the maximum permissible intake manifold pressure setting during a decrease in atmospheric pressure (increase in altitude) The spring loaded piston 3l6 acting in parallel with the power reset piston 3i 1 is employed a an altitude stop piston. This piston stops the movement of the altitude droop piston. 321 through action of member 326 so as to provide a. maximum intakemanifold pressure setting during operation of a fluid injection systemwhich i considerably greater than during non-operation of the fluid injection system.

As best shown in Figure l, the latter fluid injection system includes a conduit 350 leading from a suitable source of fluid fuel to the carburetor 62 and a conduit 35l for injecting the fuel into the induction system through a nozzle 352. There is further provided a conduit 353 for injecting into the induction system through nozzle 352 a supplemental or so-called "anti-knock fluid medium such as water, water alcohol, or other suitable fluid well known in the art for suppressing predetonation of the engine 26.

The conduit 353 is connected to a suitable metering device shown in clotted outline and indicated generally by the numeral 354. The latter metering device may be ofa suitable type well known in the art for determining the rate of flow of the supplemental fluid.

A conduit 355 leads to the metering device 354 from a suitable source of supplemental" fluid indicated by numeral 356. In the conduit 355. there is provided a pump indicated by numeral 351 driven by a suitable power means not shown. The pump 351 supplies thefluid medium under pressure to the metering device 354.

A valve 358 is provided in the conduit 355 between the pump and metering device 354 for off a and "on control of the supplemental' fluid injection system. The control valve 358 may be of any suitable type, but is shown herein as of an electromagnet controlled type having an electrical control circuit 359 and switch 360 which is preferably mounted within the aircraft cabin for convenient operation by the pilot.

Thus, thesupplemental fluid injection system may be placed in operation by the pilot closin the switch 360 so as to effect the opening of the valve 358. Conversely, the valve 358 may be closed by opening the switch 360.

A by-pass conduit 36l and relief valve 362 is provided for recirculating the fluid medium from the pump outlet to the pump inlet at such times as the valve 358 is closed and the injection system is not in operation.

A pressure switch 363 of suitable type well known in the art is further connected in conduit 355 between valve 356 and the metering device 354. The pressure switch 363 is arranged to respond to the pressure of the fluid injection system so as to close a circuit 364 for energizing the electromagnet 324 upon operation of the fluid injection system.

It will be readily seen then that upon operation of the fluid injection system, the fluid under pressure will close the pressure switch 363, whereupon valve 33l will close the open end of passage 322 The engine control unit A is l ,pistons Ill and 3" to be biased downcausi .wardly against the biasing force of the springs 3 I I1 and 3 I 3, respectively, so as to thereby increase the maximum permissible intake manifold pressure setting. Moreover. upon operation of the fluid injection system being terminated, the pressure switch 353 will open the circuit for energizing the electrom'agnet 3,24, whereupon valve 323 will open conduit 322 permitting the pistons 3l 6 and 3" to resume the normal position shown under force of springs 313 and H3 respectively. 3

Adjustable screw 313 is arranged to limit the upward movement of stop rod 320 and thereby piston 3I3, while adjustable screw 31I limits the upward movement of stop rod MI and thereby piston 3I1. By-appropriate adjustment of the screws 310 and 3', the maximum permissible intake manifold pressure, setting for non-operation'of the fluid injection system may be conveniently adjusted.

Adjustable screw 312 is arranged to limit the downward movement of stop rod 320 and thereby I piston 3I'3, while adjustable screw 313 limits the downward movement of stop ro 32I and thereby piston 3I1. By appropriate adjustment of the screws 312 and 313, the maximum permissible intake manifold pressure setting foroperation of venieritly adjusted.

' Operation 14 automatically opens the throttle 64 further to give the selected pressure. At a given position of the main control lever I the intake manifold pressure will be kept constant.

further arranged to control the operation of a variable speed supercharger drive 3I upon the throttle being adjusted to a maximum open position.-

The drive 3| includes high, intermediate and low speed hydraulic drives 39, 51 and 5|, respectively. This is accomplished through operation of a flow control valve I63. The low speed coupling the fluid injection system may likewisebe conconduit Ill and 43 to the high spee coupling Similarly, upon the supercharger 32 being driven through the coupling at a speed greater than that of the intermediatespeed coupling 51, a shut oil valve, not shown, but of a type well known in the art, closes. passage 59 and permits the intermediate speed coupling 51 to empty.

A novel reset follow-up mechanism 200 is provided arranged so as to be afl'ected by the same diflerential pressure which acts upon the metering valve I60 so as to provide a follow-up action on the servo control valve H3 to provide greater stability of control. The mechanism 200 includes a follow-up piston 202 and a reset piston 203 controlled thereby for returning the follow-up piston 202 to a neutral position and arranged to cut the follow-up piston 202 out or operation during normal throttle control. I v

The control unit A is further provided with a novel device 300 for limiting the maximum permissible selected intake manifold pressure in accordance with the prevailing atmospheric pressure or altitude and further providing means- .whereby a different limit is provided during operation of a supplemental fluid injection system than during inoperation oi the system.

5| is supplied with coupling fluid through a conduit leading from an engine driven pump and the supercharger 32 is normally driven through the low'speed coupling during operation of the throttlev 63.

However,- when the throttle 33 reaches the wide open position, the flow control valve IE0 is adjusted by increased hydraulic pressure so as to cause coupling fluid to flow through conduit I10 and line 30 to the intermediate speed coupling 51.

Upon the supercharger 32 being driven through the coupling 51 at a speed greater than that of.

low speed coupling 5|, a shut off valve, of a type 7 well known in the art, closes passage 54 and permits low speed coupling 5| to empty.

If a further increase in the speed of the supercharger 32 is required, then the flow control valve ISO is further adjusted by increased hydraulic pressure to cause coupling fluid to flow through Although only two embodiments of the invention have been illustrated and described, various changes in the form and relative arrangements of the parts may be made to suit requirements.

What is claimed is: 1. A reset follow-up mechanism comprising, in combination, a follow-up fluid motor having a piston, a reset fluid motor having a piston, an actuating rod carried by the follow-up piston, valve means mounted on, the actuating rod for controlling the reset piston, and resilient means 7 between the reset and follow-up pistons for adjustment by the reset piston to return the followup piston to a neutral position.

2. The combination defined by claim 1 in which said valve means include a pair of control valve members and a pair of metering lands controlling the flow of. pressure fluid to and from said third passage, and additional passages controlled by said valve members for by-passing said metering lands upon a relatively great changein the position of said follow-up piston.

3. The combination defined by claim 1 in which there is provided means forming a chamber n which said reset and follow-up pistons are slid- -ably positioned in longitudinal alignment, said reset piston having a greater surface area than said follow-uppiston, pressure conduits opening at opposite sides of said follow-up piston for differentially affecting said follow-up piston, one of said pressure conduits opening to one side of said reset piston, a drain conduit, and said valve means selectively controlling the opening of said drain conduit and said otherconduit to the other side of said reset piston.

4. The combination defined by claim 3 in which there is provided a stop rod for limiting the movement of one piston relative to the other and to mechanically connect the reset piston to the follow-up piston so as to return the follow-up piston and said valve means to a neutral position upon the pressure applied throughsaid one pressure conduit exceeding that in the other conduit.

5. A rest follow-up mechanism comprising, m combination, a housing having a longitudinally extending chamber formed therein, a follow-up piston slidably mounted in said chamber, a reset piston slidabiy mounted in said chamber and aligned with said follow-up piston, an actuating rod extending from one end of said follow-up piston, a stop rod extending from the other end of said follow-up piston and arranged to engage said reset piston, a helical spring surrounding said stop rod and operably connecting said reset piston to said follow-up piston, said housing having a first fluid pressure inlet passage opening into said chamber between the follow-up and reset pistons, said flrst fiuid pressure tending to bias said pistons in opposite directions, said reset piston having a greater surface area exposed to said first fluid pressure than said follow-up piston, a second fluid pressure inlet passage opening at the opposite end of said follow-up piston and opposing the force on said follow-up piston of said first fluid pressure, an inlet passage opening at the opposite end of said reset piston and onposing the force on said reset piston of said first fluid pressure, a drain passage, and valve means mounted on said actuatingrod for controlling the selective connection of said third passage to said second fluid pressure inlet passage and said drain passage so that upon movement of said followup piston, said reset piston will return said follow-up piston to a neutral position irrespective of whether said first or second fluid pressure be greater.

6. The combination defined by claim in which said valve means includes a pair of control valve members and a pair of metering lands controlling the flow of pressure fluid to and from said third passage, and additional passages controlled by said valve members for by-passing said metering lands upon a relatively great change in the position of said follow-up piston.

,7. For use with an induction system of a supercharged aircraft engine having an intake manifold, a carburetor for supplying a combustible mixture to said engine through said intake manifold, and operable means for injecting a supplemental fiuid for suppressing predetonation of said engine; the combination comprising pilot operative means for selecting a desired manifold pressure for the engine, means for controlling the manifold pressure, manifold pressure responsive means for adjusting said control means so as to maintain the selected manifold pressure, atmospheric pressure responsive means, means responsive to operation of said fluid injection means, servomotor means operably connecting said fluid injection responsive means and said atmospheric pressure responsive means jointly to said selecting means so as to vary the maximum permissible limit of the value of said selected manifold pressure in accordance with the prevailing atmospheric pressure and the operative condition of said fluid injection means.

8. For use with an induction system of a supercharged aircraft engine having an intake manifold, a carburetor for supplying a combustible mixture to said engine through said intake manifold, and operable means for injecting a supplemental fiuid for suppressing predetonation of said engine; the combination comprising pilot operative means for selecting a desired manifold pressure for the engine, means for controlling the manifold pressure, manifold pressure responsive means for adjusting said control means so as to maintain the selected manifold pressure, atmospheric pressure responsive means, a first servomotor means controlled by said atmospheric pressure responsive means, means responsive to operation of said fluid injection means, a second servomotor means controlled by said fluid in- Jection responsive means, an adjustable member positioned jointly by said first and second motor means and arranged so as to limit the: maximum permissible value of said selected manifold pressure in accordance with changes in atmospheric pressure and the operative condition of said fluid injection means.

9. The combination defined by claim 8 in which there is provided a third servomotor means for limiting the adjustment by said first servomotor means of said maximum permissible value, and said third servomotor means controlled by said fluid injection responsive means.

10. An engine control system comprising pilot operative means for selecting a desired manifold pressure for the engine, means for controlling the manifold pressure, manifold pressure responsive means for adjusting said control means so as to maintain the selected manifold pressure, atmospheric pressure responsive means, servomotor means operably connected to said atmospheric pressure responsive means, an adjustable member positioned by said motor means and arranged so as to limit the maximum permissible value of said selected manifold pressure in accordance with changes in atmospheric pressure, a pair of pistons hydraulically operated in parallel, one of said pistons limiting the adjustment of said motor means, a walking beam connecting said motor means and said other piston to said adjustable member, and valve means for jointly operating said pistons.

11. An engine control system comprising pilot operative means for selecting a desired intake manifold pressure for the engine, means for controlling the intake manifold pressure, manifold pressure responsive means for adjusting said control means so as to maintain the selected manifold pressure, said selecting means including an adjustable plate, an arm afiixed to the plate, an adjustable member for engaging said arm so as to limit the maximum selected pressure, servomotor means for positioning said adjustable member, and atmospheric pressure responsive means for controlling said motor means so as to decrease the maximum permissible selected intake manifold pressure with increase in altitude.

12. A regulator for the induction system of a supercharged aircraft engine, comprising a first piston, a second piston, a common hydraulic pressure chamber for said pistons, induction pressure responsive means for controlling the hydraulic pressure applied to said chamber, said first piston arranged to be actuated in a first sense at a first differential hydraulic pressure, said second piston arranged to be actuated in a second sense at a greater differential hydraulic pressure upon said first piston being actuated in said first sense to adjust an induction throttle valve for said engine, another member adjustably positioned by the second piston for controlling the driven speed of an engine supercharger, means for changing the datum of the pressure responsive means, a follow-up piston. hydraulically coupled in parallel to said second piston, means connecting said follow-up piston to said datum changing means so as to prevent hunting of said pressure responsive means upon a change in the greater diiierential pressure effecting said second piston, a piston for resetting said followup piston, said follow-up piston controlling the operation of said reset piston so as to effect rapid acceleration of said supercharger upon a relatively great increase in the induction pressure being required.

13. The combination defined by claim 12 including means mechanically connecting said reset and follow-up pistons so that under conditions of said first diflerential hydraulic pressure said reset and follow-up pistons may be maintained out of operation and in a neutral position.

14. A regulator for the induction system of a supercharged aircraft engine, comprising pilot operative means for selecting a desired intake manifold pressure for the engine, hydraulic motor means for controlling the intake manifold pressure, manifold pressure responsive means for adjusting said control means so as to maintain the selected manifold pressure, said selecting means including an adjustable plate, an arm afllxed to the plate, an adjustable member for engaging said arm so as to limit. the maximum selected pressure, a second motor means for positioning said adjustable member, atmospheric pressure responsive means for controlling said motor means so as to decrease the maximum permissible selected intake manifold pressure with increase in altitude, a follow-up piston operated in response to the differential pressures operating said first mentioned motor means, an actuating rod connecting said follow-up piston to said selector plate for varying the selected pressure, a reset piston, valve means mounted on the actuating rod for controlling the reset piston, and resilient wring means between the reset and follow-up pistons for adjustment by the reset piston to return the follow-up piston to a neutral position.

15. A system of control for a supercharged internal combustion engine comprising, in combination, a throttle valve controller having datum adjusting means providing for selection of an engine intake pressure to be maintained and motor means under control by the engine intake pressure and by said datum adjusting means for so positioning the engine throttle valve as to obtain th selected pressure, a control lever for operating the .datum adjusting means, a supercharger connected with the engine intake, variable speed means for driving the supercharger and having a speed changing element, said motor means under control by said engine intake pressure and by said datum adjusting means for so positioning the speed changing element asito give a supercharger speed necessary to obtain the selected pressure at varying altitudes, apparatus for effecting the injection of a liquid into the engine intake, limiting means, atmospheric pressure responsive control means to vari bly position said limiting means in proportion to said atmospheric pressure, and said limiting means normally operative by said control means to limit the selected engine intake pressure to values required for safe operation of the engine with} out liquid injection and under the prevailing ate mospheric pressure conditions, and injection liquid pressure responsive means for disabling said limiting means upon operation of said injection apparatus.

16. For use in controlling the pressure maintained in the fuel mixture intake of a supercharged internal combustion aircraft engine in which means are provided for injecting an antidetonant into said intake; a control apparatus comprising an adjustable pressure selecting memher for selecting the pressure to be maintained, atmospheric pressure responsive means, motor means controlled by said last mentioned means. stop means adjustably positioned by said motor means so as to limit the selected pressure to predetermined values variable in proportion to the prevailing atmospheric pressure conditions, means for disabling said step means including other motor means controlled by said antidetonant injecting'means to render said stop means ineilfective so as to permit said selecting means to select pressures in excess of said pre-- determined values during operation of said antidetonant injecting means.

17. The combination defined by claim 16 in which said disabling means includes an injection liquid pressure responsive switch means, electromagnetic servovalve means controlled by said switch means, and servomotor means controlled by said servovalve means for disabling said limiting means under liquid pressure conditions sufflcient to normally effect operation of the injection apparatus.

18. For use in controlling the pressure maintained in the fuel mixture intake of an internal combustion aircraft engine in which means are provided for injecting an anti-detonant into said intake and including an air inlet section, a throttle, and a variable capacity supercharging system; the combination comprising motor means for actuating the throttle and for varying the capacity of the supercharging system, means for controlling the motor means so as to maintain the engine charging pressure at a selected value, manually operable means for selecting the pressure to be maintained, a stop member for limiting the selected pressure to predetermined values for safe operationof the engine, another motor for adjustably positioning said stop member, a

; nected to said capsule for varying the position of said stop member in proportion to said variable pressure, anti-detonant pressure responsive means, and third motor means controlled by said last-mentioned means to override the second motor means and actuate the stop member to an ineffective position .during operation of said antidetonant injecting means.

HOWARD ALLAN 'ALEXANDERSON. ARTHUR HIBBARD LE FEBVRE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,187,737 Gregory Jan. 23, 1940 2,217,384 Halford et al. Oct. 8, 1940 2,284,687 Schimanek June 2, 1942 2,400,306 Hobbs May 14, 1946 2,400,307 Hobbs et a1 May 14, 1946 2,453,170 Wheeler Nov. 9, 1948 2,491,482 Dolza et al. Dec. 20, 1949 2,491,484 Dolza et al. Dec. 20, 1949 2,491,497 Jorgensen et al. Dec. 20, 1949 

